Non-woven fabrics



2,949,386 NON-WOVEN rAnnrcs Norman S. Cassel, Ridgewood, N.J., assignorto Intercilemical Corporation, New York, N.Y., a corporation of Ohio NoDrawing. Filed Nov. '3', 1958, Ser. No. 771,204 9 Claims. or. 117-140This invention relates to non-woven fabrics and aims to provide improvednon-woven fabrics especially for outer wear.

Non-woven fabrics for use as outer wear garments must be strong,durable, resilient, flexible, remain intact after washings and, ifcolored, the color should be Washfast and resistant to dry cleaning.

Thermosetting melamine-formaldehyde, urea-formaldehyde,phenol-formaldehyde and dicyandiamide-formaldehyde have been proposed asbinders for non-woven fabrics but these resins, after being thermoset,leave the fabric stiff, or boardy. Also, various thermoplastic resins orpolymers have been suggested, usually in the form of a latex. Thethermoplastics alone do not give durable bonding of the fibers to eachother. One of the best binders for making non-woven fabrics has been thesynthetic latices made by emulsion copolymerization of acrylonitrile andbutadiene. Preferably these copolymers are given a sulfur cure orvulcanization after they are applied to the web of non-woven fibers.Non-woven fabrics made in this conventional manner are strong, durable,flexible, and reasonably resistant to dry cleaning solvent, but they arenot washfast. For optimum washfastness the art has used a combination'ofthermosetting urea or melamine-formaldehyde resin with a latex of apolymer containing reactive groups. Such binder systems requirerelatively high temperatures, i.e. on the order of 350 F., to produce anon-woven fabric having good Washfastness.

It has now been discovered that non-woven fabrics having goodwashfastness and good hand can be obtained by using as a binder a latexof a polymer*con taining carboxyl groups and a particular type ofcrosslinking agent, i.e. a multifunctional monomeric material that willreact at relatively low temperatures with the polymer and thuscross-link the polymer chains with each other making the polymer evenmore insoluble. The binder system of the present invention cures to givegood washfastness at temperatures as low as 210 F. Higher temperaturescan be used however, if a shorter cure time is needed. The new bindersystem provides as good or better washfastness and hand, as any priorart process and at the same time permits greater speed and lower costsby providing a binder system that cures at a relatively low temperatureor in shorter time at the more conventional higher temperature. Thecross-linking agents that we have found to be very effective are thosecontaining three a,5-alkylene imine groups especially trialkylenephosphoramides. These cross-linking agents are preferably added to thepolymer latex prior to its application to the Web of non-Woven fibers.This formulation, containing cross-linker, cross-linkable polymer, andpigment if desired, is applied to the non-woven web in conventionalmanner as by impregnating or spraying.

States Patent woven fabrics.

or" 2,949,386 v Patented N 2 19360 The solids pick up by the fabric canbe between 15 and 200% of its weight of cross-linker plus polymer. I Itis recognized that cross-linking linear polymer systems employingpolyfunctional imine cross-linking agents have been used heretofore forproducing films, for insolubilizing resins and for preparing resins ofvarious sorts. For instance, U.S. Patent No. 2,327,760 disclosestreating a viscose fabric with an aqueous impregnating bath containingsodium polyacrylate and a difunctional imine compound. U.S. Patent No.2,341,413 describes the after-treatment with imine compoundsof fabricsthat have been previously impregnated with water-soluble coatingmaterials such as albuminous substances, cellulose compounds ofwater-soluble artificial resins. German Patent No. 896,790 describes theuse of the compound obtained by reacting one mole of phosphorousoxychloride with three moles of ethylene imine, in conjunction withpolymers containing carboxyl groups, for finishing textiles, or inconjunction with pigments, for printing or padding on textiles. GermanPatent No. 867,085 discloses cross-linking water-soluble salts of acidicpolymers 'and the use of such a system for finishing and decoratingtextiles.

None of the prior art teaches or suggests the use of the fpolyfunctionalimine's 'as binders for non-woven fabrics,

especially the advantageous results that the present applicants are ableto obtain. For instance none of the prior art would suggest or makeobvious the result that the present invention makes possible, viz. thatnon-woven fabrics having good washfastness can be obtained withoutimpairing the hand of the fabric at cure temperatures as low as 210 F.The saving in time and expense that is madepossible by the binder systemis great.

Conventional non-woven fabric webs are employed for making the non-wovenfabrics of the present invention. The webs may be made of cotton fibers,viscose rayon fibers or any of the blends with synthetic .fibers, or allsynthetics.

Typical latex polymers that are operablein the invention include thewater-insoluble emulsion copolymers of acrylic acid or methacrylic acid,maleic acid, fumaric acid, and itaconic acid, with at leastonecopolymerizable monomeric material. Such copolymerizable monomersinclude, for instance, acrylonitrile, ,methacrylonitrile,

butadiene, styrene, lower'alkyl estersof acrylic or methacrylic acid,etc. These latices are prepared in conventional manner by emulsionpolymerization using a free radical formingcatalyst. 'We prefer that themonomer containing.thefreeacidgroup compriserno more than about 7% byweight of .the total weight of ,monomers fabrics of exceptionally softhand and good washfastness.

Best resistance to alternate light wash is obtained by including25 to 35percent vacrylonitrileras a monomer. Quite desirablearesults are alsoobtained 'using 1-,3-butadiene :'acrylonitrile:methacrylicacid-.copolymers such 18S Hycar 1571. This latter'materialis typical ofthe latex polymers that are used in the trade as binders fornon-Conventional vulcanizing agents or zinc oxide are recommended in thetrade as curing agents for this binder. The present invention providesan improvement inthispriorpractice in -that.the use ,of trialkylenephosphoramide as the cross-linking agent for the Hycar 1571 latextypeofnon-woven fabric binder gives a non-Woven fabric having improvedwashfastness.

nating bath at 35% solids instead of 12%.

Example 1.A non-woven cotton fabric (85 grams/sq. yd.) made of randomlydistributed intersecting fibers impregnated by immersing it in anaqueous composition of 12% solids, the solids consisting of a mixture of100 parts of a 53.5 :43.5 :3 butadiene:acrylonitrilezmethacrylic acidemulsion copolymer, parts tripropylene phosphoramide and 1.12 partsofsodium alginate (used as a migration contfol agent) The fabric wasremoved from the composition and the excess impregnant removed byrunning it between rubber-squeeze rolls adjusted to give a dry weightpick up on the fabric of 25-30% The fabric was dried and cured byplacing in a circulating hot air oven at 280 F. for 5 minutes. A sampleof the material, when subjected to an Accelerated Wash Fastness Test(Number 3A, under Standard Test Method 61-54 as outlined in theTechnical Manual and Year Book of the American Association of TextileChemists and Colorists) showed excellent washfastness compared to asimilar fabric which had been given asimilar treatment with animpregnating composition containing conventional rubber curingagents,i.e. 0.5 part ammonium caseinate, 5.0 parts zinc oxide, 2.0 partssulfur and 2.0 parts zinc diethyIdithiocarbarnate, instead of thetripropylene phosphoramide. Curing for 20 minutes instead of 5 minutesat 280 F. gave the same results. i I

Example 2.--The above example was repeated except that 1 part oftripropylene phosphoramide was used instead of 5 parts. There was only aslight loss of color when the fabric was subjected to a No. 3A washtest. A fabric similarly treated except that no cross-linking agent waspresent in the impregnating bath resulted in a fabric that completelydisintegrated when subjected to the No. 3A wash test.

Example 3.Example 1 was repeated using 3 parts of tripropylenephosphoramide instead of 5 parts and this resulted in a fabric havingexcellent washfastness when subjected to a No. 3A washfastness test.

Example 4.Exarnple 1 was repeated using 5 parts of tripropylenethiophosphoramide instead of 5 parts of tripropylene phosphoramide. Theresulting fabric showed only a slight loss in color when subjected to aNo. 3A wash test.

Example 5 .-Example 1 was repeated using a 60:35:5 emulsion copolymer ofbutyl acrylate:acrylonitrile:methacrylic acid instead of thebutadiene:acrylonitrilezmethacrylic acid copolymer. The non-woven fabricobtained had excellent washfastness when subjected to a No. 3A wash testand the fabric had excellent hand and was also non-yellowing.

Example 6 .Example 1 was repeated using the impreg- This resulted in a100% by Weight pick-up by the fabric. The fabric had excellentwashfastness but was slightly stiffer than the fabric of Example 1.

Example 7.--A non-woven viscose fabric made up of oriented overlappingintersecting viscose fibers and weighmg 400 grains per square yard wasimpregnated with a composition consisting of (1) 63.5 parts of a 37%solids latex of copolymer containing 90% ethyl acrylate, 5%acrylonitrile and 5% methacrylic acid, (2) 2.5 parts of tripropylenephosphoramide and (3) 34 parts of water. The impregnated fabric waspassed between squeeze rollers adjusted to give a pick-up of impregnantof 25% of the weight of the web (dry basis). After can drying for onemlnute at 210 F. the fabric was aged at room temperature for 24 hours.The fabric had excellent washfastness for its weight (e.g. withstandsAATCC #2 Wash) and tensile strength. Its tensile strength is equal tothe tensile strength of a similar non-woven fabric made w1th 50% drypick-up of polyvinyl acetate (a conventional non-woven fabric binder).The fabric made with polyv1nyl acetate as binder was also stiffer thanthe product of th s example and had no detectable washfastness. Thenon-woven fabric of this example was non-yellowing when exposed to heator light (Fadeometer).

4 Example 8.A non-woven web made up of randomly distributed cottonfibers was impregnated (35% dry pickup) in a bath consisting of PartsPhthalocyanine blue pigment (added as a 16% aqueous dispersion) 3.0 37%latex (95:5 ethylacrylate:methacrylic acid copolymer) 75.00 Tripropylenephosphoramide 2.0 Water 20.00

Parts Phthalocyanine blue pigment (as a 16% aqueous dispersion) 3.00 37%latex (60:35:5 copolymer butyl acrylate:

acrylonitrilezmethacrylic acid) 80.00 Tr'propylene phosphoramide 1.50Water g 15.50

After can drying one minute at 210 F. the fabric was given an additionalcure of three minutes at 300 F.

The resulting fabric had fastness properties similar to those for thefabric produced in Example 8.

The main purpose for adding the blue pigment to the impregnating bathsin the above examples was to make it possible to observe the tendency ofthe binder to migrate on drying, but from these examples it is obviousthat pigments and dyes could be used with the binder so that coloringand binding can be achieved in a single operation. If migration of thebinder becomes a problem, so that even distribution of binder over theWeb is not obtained, it can be largely overcome by the addition of asmall amount of sodium alginate to the bath.

I claim:

1. A non-woven fabric comprising a web of overlapping intersectingfibers uniformly bonded with a binder formed in situ by cross-linking alinear polymer containing carboxyl groups with a polyfunctional iminecross-linking agent.

2. A non-woven fabric comprising a web of overlapping intersectingfibers uniformly bonded with 5 to 200% of its weight of a cross-linkedpolymer formed by crosslinking a linear polymer containing carboxylgroups with an imine cross-linking agent.

3. A non-woven fabric as in claim 2 wherein the binder is formed bycross-linking a linear copolymer containing 1 to 7% of copolymerizedmonomer of the group consisting of acrylic acid and methacrylic acid.

4. A non-woven fabric as in claim 2 wherein the imine cross-linkingagent is a trialkylene phosphoramide having the structure Where R is amember of the group consisting of hydrogroup consisting of butadiene andbutyl acrylate, and 0 to 35% acrylonitrile with 1 to 5% of its weight ofa polyfunctional imine of the formula:

where R is selected from the group consisting of hydrogen, methyl andethyl.-

6. A non-Woven fabric as in claim 5 wherein the polyfunctional amine istripropylene phosphoramide.

7. A non-woven fabric comprising a web of overlapping intersectingfibers bonded together with 5 to 200% of its weight of a binder fiormedby cross-linking a linear addition polymer containing 1 to 7% by weightof methacrylic acid, 0 to 35% by weight of 'acrylonitrile and 60 to 95 6parts of butyl acrylate, with 1 to 5% of its weight of tripropylenephosphoramide.

8. The process for making non-woven fabric which consists of (1)uniformly applying to a web of overlapping intersecting fibers 5 to 200%by weight of crosslinkable binder consisting of to 99 parts of acrosslinkable linear addition polymer and 1 to 5 parts of an imine(moss-linking agent and (2) heating the web and binder to causecross-linking of the polymer and crosslinking agent. I

9. A process as claimed in claim 8 wherein the crosslinking agent istripropylene phosphor-amide.

References Cited in the file of this patent UNITED STATES PATENTS2,676,128 Piccard Apr. 20, 1954 2,698,574 Dougherty et a1. Ian. 4, 19552,719,806 Nottebohm Oct. 4, 1955 2,774,687 Nottebohm Dec. 18, 19562,823,142 Sumner et a1. Feb. 11, 1958

8. THE PROCESS FOR MAKING NON-WOVEN FABRIC WHICH CONSISTS OF (1)UNIFORMLY APPLYING TO A WEB OF OVERLAPPING INTERSECTING FIBERS 5 TO 200%BY WEIGHT OF CROSSLINKABLE BINDER CONSISTING OF 95 TO 99 PARTS OF ACROSSLINKABLE LINER ADDITION POLYMER AND 1 TO 5 PARTS OF AN IMINE TOCAUSE CROSS-LINKING AGENT (2) HEATING THE WEB AND BINDER TO CAUSECROSS-LINKING OF THE POLYMER AND CROSSLINKING AGENT.